The invention relates to a method for continuously monitoring vehicle function components through the use of a diagnostic device taken along in the vehicle and, in particular, to monitoring function components relevant to exhaust gases, using a multiplicity of single test routines which are successively pending in a prescribed cyclic sequence. Each test routine is respectively activated only in the presence of interrogatable start conditions specific to the test routine. Such a diagnostic method is used, for example, for continuously monitoring vehicle function components, relevant to exhaust gases, in the running operation of the vehicle.
Ever more complex electronic control components have been used recently in motor vehicles, for example for fuel injection, for ABS and ASR systems, for automatic transmissions, and the like. This has produced the need to be able to test such vehicle function components quickly and cost-effectively and, as the case may be, to repair them. The known workshop manner conventionally used for testing and repair have quickly proved to be unsatisfactory for this purpose. One reason for this is that although important information on the sequence of the functions, for example, manipulated variables, filed in a control device are present in the computer of the control device, they cannot be rendered accessible using the conventional workshop techniques. This made it necessary to develop diagnostic systems and diagnostic methods which are adapted to modern vehicle electronic systems.
Customary known diagnostic systems can be subdivided into external, so-called off-board diagnostic systems and vehicle-mounted, so-called on-board diagnostic systems. In the off-board diagnostic systems an external diagnostic device is connected, for example on the workshop side, to the vehicle electronics. The diagnostic method is stored in the external diagnostic device. After the connection, the stored diagnostic method is carried out with the motor running. Such diagnostic systems are disclosed, for example, in German Patent documents DE 39 04 915 C2 and DE 39 32 436 C2.
In the case of an off-board diagnostic system specified in the German Patent document DE 32 29 411 A1, an external test unit signals to a control device, located inside the vehicle electronics and capable of being connected to said test device, via a test connection that a fault monitoring procedure filed there as a program in a memory is to be carried out a central processing unit of the vehicle electronics. Thereafter, a series of test points which are identified with the aid of the input signals are tested. The test program, that is to say the diagnostic method, is always carried out when the central processing unit is not occupied with vehicle electronics control programs, such as engine control programs. After each execution of the test program, the respective test result is retrievably stored in a nonvolatile memory. All the test routines are carried out in a prescribed, fixed sequence, as filed in the relevant memory.
By contrast, on-board diagnosis has recently been preferred, since it very effectively permits vehicle function components to be continuously monitored on board in the vehicle during driving operation. It is precisely this type of monitoring which is even partially prescribed by statute, for example in the State of California in the United States for relevant exhaust gas systems and components in passenger cars.
In a diagnostic system for a motor vehicle, disclosed in German Patent document DE 35 40 599 A1, off-board or on-board diagnosis is possible in an optionally switchable fashion. A switching capability, which can be operated by the user, is proposed for the on-board diagnostic method, in order to activate an automatic, sequentially proceeding diagnostic sequence of test routines which are prescribed in a fixed fashion. Faults which have respectively occurred are displayed for some time or are reproduced on an external logging unit. The known diagnostic system is intended to permanently detect general and/or safety-relevant system defects in the control systems or function systems and/or other vehicle components during driving as well, and to display them to the driver while driving. In order to carry out the diagnostic method, a test unit which contains, in particular, a microcomputer and further customary peripheral components, is arranged inside the vehicle electronics. In particular, memories are present in which, inter alia, the fixed sequence of the test routines to be carried out is stored.
German Patent document DE 37 26 344 C2 discloses a diagnostic system for control devices of a motor vehicle, in which there are stored in a respective control device diagnostic routines. The diagnostic routines can be activated for vehicle components driven by this control device. In this case, a priority sequence is prescribed in each case both for the selection of the respective control device by a diagnostic computer integrated in the vehicle or an external diagnostic device for diagnostic purposes, and for carrying out the diagnostic routines inside a control device. Using different diagnostic control pulses, it is possible in accordance with this priority sequence both to progress inside a control device from one diagnostic routine to the next and to progress from one control device to the next. It is further possible to skip diagnostic routines that are not to be executed. The faults detected in each case by a control device are reported and displayed by the control device and are stored by it in a fault memory of the diagnostic computer or of the diagnostic device.
German Patent document DE 32 31 398 A1 describes a data acquisition system for vehicles which contains a device, installed in the vehicle, for cyclic acquisition of the data from transmitters which detect the dynamic vehicle variables of specific vehicle states. The data acquisition system further includes a cassette for data storage which can be inserted into the device, and a computer for receiving and processing the data stored in the cassette. In order for the vehicle owner to flexibly determine which of the data acquired by the transmitters are respectively to be evaluated, the computer provides the data memory of the cassette with selection information which can be prescribed by the vehicle owner. With the aid of this selection information, the data acquisition process is then carried out according to a prescribed data acquisition routine which contains, inter alia, an interrogation of the individual transmitter data in a predetermined sequence.
In present on-board diagnostic systems, the checking of sensors, actuators and further function components as a function of the desired test thoroughness requires a set of individual test routines. The number of test routines is frequently greater than 50 in the case of modern systems. However, given such a large number of test routines, of which frequently a plurality can be carried out under the same start conditions but not simultaneously, it is not very effective to process these test routines in accordance with a sequence which is prescribed in a fixed fashion.
There is therefore needed a method for continuous, on-board monitoring of vehicle function components using a diagnostic device which is taken along in the vehicle. By use of the diagnostic device, the method must perform a multiplicity of test routines effectively and must permit as quickly and reliably as possible the determination of a statement as to whether all the monitored function components are operating properly.
These needs are met according to the present invention by a method for continuously monitoring vehicle function components using a diagnostic device taken along in the vehicle, in particular to monitoring function components relevant to exhaust gases, using a multiplicity of single test routines which-are successively pending in a prescribed cyclic sequence. Each test routine is respectively activated only in the presence of interrogatable start conditions specific to the test routine. An item of data information relating to whether a respective test routine has been carried out at least once in the current operating phase is retrievably stored in a memory. Before activation of a test routine pending according to the prescribed sequence, by retrieving the appropriate stored data it is detected whether this test routine has already been carried out at least once before and whether at least one other test routine exists whose start conditions are present and which has so far not yet been carried out, whereafter the pending test routine is activated when this is not the case. The at least one other test routine so far not yet carried out is activated when this is the case.
The processing of the test routine sequence is thereby flexibly configured, since it is possible to deviate from the prescribed sequence when it is established upon appropriate interrogation of memory contents, that a pending test routine has already been carried out once and, by contrast, another test routine whose start conditions are present has so far not yet been carried out. The memory contents are provided in memories arranged in the vehicle. Instead of once again carrying out the pending routine, in this case a jump is made in the test routine sequence to the test routine that has not yet been carried out, and the latter is carried out for the first time. This procedure guarantees that in the case of a multiplicity of test routines, each test routine is carried out at least once after a comparatively short time, after which detailed information is then present regarding the presence or absence of system faults with respect to all the monitored function components.
A further embodiment of the invention permits so-called secondary fault exclusion, that is to say, blocking an evaluation of the respectively activated test routine and of test routines dependent on the result thereof makes it possible to trace faults in the presence of implausible values of input variables, and only causal faults are recorded. This has the result that fault localization is not complicated by an abundance of secondary faults.
In accordance with a still further embodiment of the invention, it is preferred for the presence of a fault not to be signalled until the ratio of test results of a test routine which are indicative of a fault to those which are not indicative of a fault and were acquired over a prescribed period exceeds a prescribable limiting value. As a result, so-called fault debouncing is realized, that is to say, not every implausible state or measured value detected by carrying out a test routine is immediately declared as a fault, but it is not concluded that there is a fault until there is sufficiently frequent confirmation of such implausible states or measured values.
Another advantageous embodiment of the invention permits the generation of a readiness identifier, in which a retrievable item of information indicating that each test routine has already been carried out at least once. Thus, for example, it is possible to indicate to the user whether test results have already been generated for all monitored function components in the current operating phase, and therefore whether reading out an available fault memory at the respective instant is sensible or not.
A further advantageous embodiment of the invention is in particular, in conjunction with an additional connectable off-board diagnostic system, since such monitoring is greatly eased by the presence of environmental data, for example, data relating to vehicle speed, motor speed, load, coolant temperature, route, duration of the current operating phase and operating states of the control loop which characterize the system state in the case of the first and of the respectively last occurrence of the fault or of an implausible state or measured value. At the same time, there is not an excessive demand on storage space because of the restriction to storage of the data in the case of the first and in the case of the respectively last occurrence of a fault.
As a result of a further embodiment of the invention, a warning lamp provided for the driver is activated by the vehicle diagnostic system, which is carried out automatically, only when a respective fault is present in different situations with sufficient probability.